So here's the deal -- whether you're using a mag-mount or a trunk / lip mount, your mobile antenna should be NMO. NMO mounts are designed to repel moisture better, and to withstand greater loads of wind sheer. Let me tell you a story...

When I was licensed 13 years ago, I was 20 years old. I had REALLY long bright red hair (natural color, I'm a ginger), played in a metal band (guitar), and drove a Mustang (to get bitches). My Mustang had a Diamond NMO mag-mount with an SG7500NMO whip. Quality gear for a college kid, right?

I put 130,000 miles on that antenna, often at speeds WELL in excess of 100 mph. No issues. You want a field testimonial? There you go. I ran that car up and down every freeway in Northeast Ohio for 5 1/2 years, including through Winter slush / salt / snow season (ever heard of "lake effect snow?"), and that antenna was still in champion form when I took it off to junk the car after it blew up.

Years later, when it was time to put an antenna on my little Mazda, it was a no-brainer to go back to Diamond for a new SG7500NMO, but this time I went trunk mount, because the pony had a rust circle started under the magnet when I took it off. The SG7900NMO is too tall for a car you'll be driving into parking garages and such, and you don't want to go banging a $100 antenna off the ceiling and pipes. Trunk-mounted SG7500NMO clears easily.

My Jeep, however, was a different story. Over there, I wanted the rawest highest-gain highest-performance antenna in sight, so the SG7900NMO won out. Cool feature: both of them fold down for easy storage in low-clearance areas. Performance is outstanding, wind shear at speed is a non-issue, they even look sharp, if you need a hand, Diamond's customer support is outstanding. SWRs are 1:1.5 at band edges and 1:1.1 through common input frequency ranges, with the exception of 444.000 and higher UHF repeater inputs because, duh, that's at the band edge.

Highly recommend these antennas over all others. Sometimes you really do get what you pay for.

I got my cheap Diamond VHF/UHF MR73 today. I chose this because the nagoya 771 whip is pretty cumbersome to handle in the car.It seems they are almost the same in performance. I use it with my Baofeng. It's small and inconspicuous. I could easily reach the next repeater 30 miles away on low. Although it's not an extremely high gain antenna it does the job for now. The UHF reception is awesome though, I could listen to local chatter although I was driving through a canyon.